Embodiments of the inventive concepts described herein relate to a time digital converter, and more particularly, relate to a gated-ring-oscillator-based time-to-digital converter.
A gated-ring-oscillator-based time-to-digital converter may sample an output signals of delay cells of a gated ring oscillator to convert an enable signal generated by a time difference between a start signal and a stop signal into a digital code. The gated-ring-oscillator-based time-to-digital converter may perform first-order shaping about quantization noise. The gated-ring-oscillator-based time-to-digital converter may have excellent low noise and linearity characteristics.
That is, since the gated-ring-oscillator-based time-to-digital converter holds a state between measurement periods to transfer an error to a next measurement periods, the gated-ring-oscillator-based time-to-digital converter may have a first noise shaping characteristic where the whole quantization error value of a measurement period appears as a difference between next quantization error and previous quantization error, thereby reducing quantization noise.
However, a conventional gated-ring-oscillator-based time-to-digital converter may have a disadvantage in that resolution is restricted to a value corresponding to a delay time of an inverter (or a delay cell) of a gated ring oscillator.